Related papers: Chiral Symmetry and Scalar Meson in Hadron and Nuc…
It is pointed out that the hadron spectroscopy should be a study of the structure of the QCD vacuum, low-energy elementary excitations on top of which are hadrons. Concentrating on the dynamical breaking of the chiral symmetry in the QCD…
We generalize the linear sigma model in order to develop a chiral-invariant model of nuclear structure. The model is natural, and contains not only the usual sigma meson which is the chiral partner of the pion but also a new chiral-singlet…
We first review the recent accumulating evidences of the existence of a scalar-isoscalar meson with the mass 500 to 800 MeV which may be identified with the sigma meson as the quantum fluctuation of the amplitude of the chiral order…
Chiral theories with spontaneous symmetry breaking such as the Nambu-Jona-Lasinio (NJL) model lead to the existence of a scalar mode. We present in a detailed manner how the corresponding low momentum effective lagrangian involving the…
We compare two QCD-inspired quark models with four-fermion interaction, without and with the remnant coupling to low-energy gluons, in the regime of dynamical chiral symmetry breaking (DCSB). The first one, the Nambu-Jona-Lasinio (NJL)…
After a brief overview of the realization of chiral symmetry in hot and/or dense medium, the implications of the existence of a light scalar-isoscalar meson (which we call $\sigma$ throughout this report) are discussed in the vacuum and in…
Recent theoretical developments of hadrons in nuclei are briefly reviewed in the aspect of chiral symmetry in nuclei. We show a general sum rule connecting in-medium hadronic quantities and quark condensate, emphasizing that both pionic…
Some issues on the low-mass scalar mesons are discussed in relation to the chiral transition of QCD vacuum. The importance to explore the possible collective nature of the $\sigma$ meson is emphasized in association with the chiral…
The Chiral Quark-Soliton Model of nucleons is based on two ideas: 1) the major role of spontaneous chiral symmetry breaking in hadron physics and 2) the relevance of the large number of colours limit for the real world. In these lectures I…
It should be a typical subject in this workshop to explore possible change of hadron properties in association with that of QCD vacuum due to an environmental change. In this report, we first summarize what hadrons are expected to show such…
We discuss how the possible changes of hadron properties can be tested, associated with the chiral transition in nuclear medium; the hadrons discussed are the vector mesons,the $\sigma$ meson and the chiral partner of the nucleon. We…
We investigate an extended chiral soliton model which includes $\pi, \rho, \omega$ and $\sigma $ mesons as explicit degrees of freedom. The Lagrangian incorporates chiral symmetry and broken scale invariance. A scalar-isoscalar meson…
We discuss the possible influence of fundamental QCD properties such as spontaneous chiral symmetry breaking and nucleon substructure on nuclear matter properties. We propose a chiral version of the relativistic $\sigma-\omega$ model in…
We first note the peculiar property of the pion as the pseudoscalar particle, which play the essential role in realizing the basic properties of the nuclear matter such as the density/energy saturations. Then, we introduce the notion of…
We first discuss the theoretical and phenomenological significance of the sigma meson ($\sigma$) in QCD. It is indicated that if the collective modes with the mass 500-600 MeV exists in the $I=J=0$ channel, various empirical facts in hadron…
An effective hadronic lagrangian consistent with the symmetries of quantum chromodynamics and intended for applications to finite-density systems is constructed. The degrees of freedom are (valence) nucleons, pions, and the low-lying…
When a light scalar dilaton $\sigma$ and the light-quark vector mesons $V=(\rho,\omega)$ are incorporated into an effective scale-invariant hidden local symmetric (sHLS) Lagrangian, scale symmetry for $\sigma$ and local gauge symmetry for…
Within a chiral quark sigma model in which quarks interact via the exchange of sigma and pi-mesons, hadron properties are investigated. This model of the nucleon and delta is based on the idea that strong QCD forces on very short distances…
An analysis of nuclear properties based on a relativistic energy functional containing Dirac nucleons and classical scalar and vector meson fields is discussed. Density functional theory implies that this energy functional can include…
We review recent developments in exploring possible precursory phenomena of partial restoration of chiral symmetry in nuclear medium by examining the spectral function in the scalar channel. We emphasize that the wave function…